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Expanded Populations of Surface Membrane Immunoglobulin Light Chain–Negative B Cells in Lymph Nodes Are Not Always Indicative of B-Cell Lymphoma

Xian-Feng Zhao MD, PhD, Sindhu Cherian MD, Rachel Sargent MD, Raja Seethala MD, Hugh Bonner MD, Bernard Greenberg MD, Adam Bagg MD
DOI: http://dx.doi.org/10.1309/5R76B01VCATQLBK6 143-150 First published online: 1 July 2005


Immunophenotypic analysis is useful in distinguishing reactive from neoplastic lymphoproliferations, particularly when tissue is limited or histologic findings are equivocal. Surface membrane immunoglobulin (SmIg) light chain restriction in B cells is especially helpful in documenting clonality, and the loss of SmIg by B cells in extramedullary sites also has been used as a criterion to support the presence of lymphoma. However, we identified 3 cases of benign follicular hyperplasia (in 101 cases analyzed) with profound expansions (56%–88% of the B cells) of SmIg light chain–negative B cells without clonality by immunoglobulin heavy chain gene polymerase chain reaction. Thus, although uncommonly encountered, lack of SmIg light chain expression by B cells should not necessarily be interpreted as indicative of lymphoma. Interestingly, 2 of the 3 patients with these “aberrant” expansions were HIV+, and such patients are at heightened risk for the development of lymphoma. Therefore, there is the potential for misdiagnosing lymphoma if flow cytometric data are interpreted inappropriately in isolation.

Key Words:
  • Flow cytometry
  • Surface membrane immunoglobulin-negative
  • B cells
  • Florid follicular hyperplasia